This application is based on Japanese Patent Application No. 10-36314 filed on Feb. 18, 1998, the entire contents of which are incorporated herein by reference.
a) Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device using a ferroelectric film and the device manufactured thereby, more particularly to a method of manufacturing the device whose ferroelectric film is coated with a protection film, and the device manufactured thereby. For example, the ferroelectric film is used as a dielectric layer of a ferroelectric capacitor incorporated in a semiconductor integrated circuit.
b) Description of the Related Art
A non-volatile memory device having ferroelectric capacitors has been used in an IC card, or the like. Because the characteristics of a ferroelectric material deteriorate when it is exposed to a hydrogen atmosphere, it is preferred that the ferroelectric material be manufactured under an atmosphere with little hydrogen. An SiN film is used as a protection film of a regular semiconductor integrated circuit. The ammonia gas is used as a source gas for depositing the SiN film under high temperature. Therefore, the SiN film is not suitable for the protection film of the integrated circuit having the ferroelectric capacitors. An SiO2 film which is deposited by means of a diode parallel plates plasma CVD apparatus is usually used for the protection film.
A conventional protection film does not completely prevent the ferroelectric film from deteriorating, therefore, the deterioration of the electric characteristics of the ferroelectric capacitor often occurs.
An object of the present invention to provide a method for forming a protection film which can prevent a ferroelectric film from deteriorating, and a device using the protection film.
According to one aspect of the present invention, there is provided a method for manufacturing a device using a ferroelectric film, the method comprising a forming step of forming a ferroelectric film on a principal surface of an underlying substrate, and a depositing step of depositing an insulating protection film so that the ferroelectric film is covered with the protection film, by a vapor deposition process using high density plasma.
The density of the protection film deposited with the high density plasma is high, and thus deposited protection film has high moisture resistivity.
According to another aspect of the present invention, there is provided a method of manufacturing a device using a ferroelectric film, the method comprising a forming step of forming a ferroelectric film on a principal surface of an underlying substrate, a heating step of heating the underlying substrate and the ferroelectric film, and a depositing step of depositing a protection film after the heating step so that the ferroelectric film is coated with the protection film, without exposing the underlying substrate to the atmosphere.
The heating of the underlying substrate before the protection film deposition evaporates the moisture on the substrate. As a result, the ferroelectric film is prevented from deteriorating.
According to still another aspect of the present invention, there is provided a method of manufacturing a device using a ferroelectric film comprising a forming step of forming a ferroelectric film on a principal surface of an underlying substrate, and a depositing step of depositing a protection film of fluorine added silicon oxide so that the ferroelectric film is coated with the protection film, using source gases each having no bonding of with Si and H.
Using the gases without bonding of Si and H prevents the protection film from taking the hydrogen atoms therein. Reduction of hydrogen in the protection film mitigates a bad influence upon the ferroelectric film in the manufacturing steps which occur afterwards.
According to a further aspect of the present invention, there is provided a device using a ferroelectric film, the device comprising an underlying substrate having a principal surface, a ferroelectric film formed on the principal surface of the underlying substrate, and a protection film of silicon oxide formed so that the ferroelectric film is coated with the protection film wherein peak height of the Fourier transform infrared spectroscopy which corresponds to bonding of Si and H is lower than 2% of maximum peak height corresponding to bonding of Si and O.
Reduction of the hydrogen in the protection film mitigates a bad influence upon the ferroelectric film in the manufacturing steps thereafter.
According to a still further aspect of the present invention, there is provided a device using a ferroelectric film, the device comprising an underlying substrate having a principal surface, a ferroelectric film formed on the principal surface of the underlying substrate, and a protection film of fluorine added silicon oxide formed on the ferroelectric film.
If an SiF4 gas is used as a source gas for depositing a protection film comprising Si. Thus deposited protection film takes fluorine atoms therein. In this case, the quantity of hydrogen atoms in the protection film is reduced to less than that of a protection film deposited with a source gas such as SiH4 which includes hydrogen atoms.
As described in the above, a ferroelectric film is coated with a protection film having high moisture resistivity so as to be prevented from being moistened. Thus, the ferroelectric film is prevented from deteriorating. In the case of a capacitor using the ferroelectric film, the characteristics of the capacitor is prevented from deteriorating.